Braverman–Kazhdan local ρ\rho-Fourier transform conjecture

Let GG be a reductive group over a local field FF, assume that there is an exact sequence

1GGGm11\to G'\to G\to \mathbb{G}_m\to 1

with nontrivial homomorphism ν:GGm\nu:G\to\mathbb{G}_m, and let ρ:LGGL(Vρ)\rho:{}^LG\to\operatorname{GL}(V_\rho) be irreducible with ρν\rho\circ\nu^\vee acting by scalar multiplication. Set

nρ=2ηG,λρ+1,n_\rho=\langle 2\eta_G,\lambda_\rho\rangle+1,

where 2ηG2\eta_G is the sum of the positive roots and λρ\lambda_\rho is the highest weight of ρ\rho, and define the local zeta integrals, basic function, invariant distribution, and ρ\rho-Fourier transform as in the statement below.

Braverman–Kazhdan local ρ\rho-Fourier transform conjecture. There exist a ρ\rho-Schwartz space, a distinguished ρ\rho-basic function, and an invariant distribution satisfying all the listed properties: meromorphic continuation and Langlands local LL-factor generation for the zeta integrals; the stated basic-function identities; the Bernstein-centre and gamma-factor properties of the distribution; and an invertible ρ\rho-Fourier transform

Fψρ(ϕ)(g)=ν(g)nρ(Jψρϕ)(g)\mathcal{F}^{\rho}_{\psi}(\phi)(g)=|\nu(g)|^{-n_\rho}(J^{\rho}_{\psi}*\phi^\vee)(g)

that preserves the Schwartz space, satisfies

FψρFψ1ρ=Id,\mathcal{F}^{\rho}_{\psi}\circ\mathcal{F}^{\rho}_{\psi^{-1}}=\operatorname{Id},

is unitary on L2(G(F),ν(g)nρdg)L^2(G(F),|\nu(g)|^{n_\rho}\,\mathrm{d}g), fixes the basic function, and gives the functional equation

Z(1s,Fψρ(ϕ),φπ)=γ(s,π,ρ,ψ)Z(s,ϕ,φπ).\mathcal{Z}(1-s,\mathcal{F}^{\rho}_{\psi}(\phi),\varphi_\pi^\vee)=\gamma(s,\pi,\rho,\psi)\mathcal{Z}(s,\phi,\varphi_\pi).

This is the local aspect of the Braverman–Kazhdan program. The statement packages analytic continuation, local factors, gamma factors, and Fourier duality into one proposed framework; the source presents it as a conjectural proposal rather than a theorem.

Sources & referencesView supporting material

Primary source

Zhilin Luo and Ngo Bao Chau, “Nonabelian Fourier Kernels on SL_2 and GL_2”, arXiv:2409.14696 (2024).

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